After dismissing "right-wing crazies" who reject mainstream climate science, Bloomberg was asked by CNN's Christiane Amanpour what he made of the GOP field.

The billionaire media mogul, who has championed the issue of climate change, first criticized retired neurosurgeon Ben Carson.

"There's one of them who was a surgeon, unfortunately at Johns Hopkins, who doesn't believe in science," Bloomberg said. "Somebody said that's like a business executive that doesn't believe in profits."

Bloomberg then said that Sen. Ted Cruz of Texas had said some of the "stupidest" things about climate change despite his intellect. He noted that Cruz's intelligence had been praised by Alan Dershowitz, a prominent US attorney who was once Cruz's Harvard professor.

"You've got a guy like Ted Cruz — who I think Dershowitz said was the smartest law student he ever had — and he says some of the stupidest things I've ever heard," Bloomberg said. "The only explanation — the only explanation — is he doesn't believe it; he's just saying it."

He added: "Ted Cruz is a smart guy, and you can't say what he says in an intelligent way."

Cruz, who has surged in recent primary polls, has not shied away from criticizing mainstream climate science.

"If you look at satellite data for the last 18 years, there's been zero recorded warming," Cruz said in August, according to Time magazine. "The satellite says it ain't happening ... I'm saying that data and facts don't support it."

Reached for comment on Bloomberg's criticism, Cruz campaign spokesman Rick Tyler dismissed the former mayor as a "myopic" elitist.

"The myopic Mr. Bloomberg should look past his armed guards and beyond his cloistered circumstances and take in a big gulp of reality," Tyler told Business Insider. "Most of what Ted Cruz says is simple common sense. Most of what Mr. Bloomberg says defies logic."